The assembly or disassembly of sealless magnetic drive pumps, i.e., pumps which have complementary and mutually magnetically-attractive, magnet-carrier assemblies, can prove difficult. This is due to the very high attractive forces which can be created by the magnets of the carrier assemblies. These forces increase significantly with larger magnet drives due to the increased magnet volume used. Current assembly or disassembly practices do not provide a means for keeping the outer magnet-carrier reasonably concentric with the inner magnet-carrier. Some reasonable concentricity is necessary to avoid contact between the outer magnet-carrier assembly and the containment shell, thereby preventing a safety hazard or damage to the equipment.
In current practice, during assembly of the magnet drive end of the pump over the magnet driven end, the drive end, having the outer magnet-carrier assembly, is contacted with the containment shell outer surface, and then is slid forward, into the driven end portion of the housing, until it is fully engaged with the inner, driven end assembly. This practice has serious shortcomings. The magnets are formed of ceramic material and, therefore, are inherently brittle. Any contact between mating parts, during the slidable installation, can cause chipping of the magnets. High magnetic forces are experienced, both radially and axially, when assembling or disassembling the magnet drives. In that containment shells are relatively thin, typically less than one-sixteenth of an inch, damage may occur thereto if the outer magnet-carrier assembly forcefully contacts it. Further, some designs use ceramic or plastic containment shells which, potentially, could crack upon impact. Safety hazards can be created if mating components slam together, during assembly and/or disassembly, trapping and injuring fingers. Also, once the magnet drive end has been assembled to the magnet driven end, the true mating of the rabbet fit, which ultimately aligns the two components concentrically, can be awkward and difficult to effect, due to the radial pull of the inner and outer magnets.